Serving fries from a food truck would have been a futile effort under Chicago's former regulations. Who wants to eat a pre-packaged batch that's fried in the morning and sits under heaters all day? After an ordinance allowing on-board cooking passed last year, licensed trucks are free to cook to order. We paid a visit to two recently debuted trucks that are frying up their own signature versions.

Jerk fries ($3) at Jerk Modern Jamaican Grill

The backstory: Video game producer-turned-food truck operator Dion Solano's two-month-old truck is inspired by the food carts he ate from growing up in Jamaica.

Best for: Eating on the go. Though the name might sound like the fries are covered with sloppy jerk sauce, they're actually just coated in jerk seasoning before being tossed into a wax paper bag, which makes for easy snacking-while-walking.

Tasting notes: Solano dusts his fries with the same jerk seasoning he uses on his meats. It's peppery, salty and sweet and built a slow burn with every fry I popped into my mouth. He keeps the exact spice mix under wraps, but the lettering on the back of the truck—"Vehicle powered by allspice"—provides one clue.

The backstory: Husband-and-wife team Sarah Weitz and Sam Barron (a former sous chef at Pump Room) sampled street food around the world while working on organic farms and now are putting their own spin on classic sandwiches with this three-week-old truck.

Best for: Eating right away. When packaged up to-go, the cheesy, greasy deliciousness of these fries soaks through the cardboard boat they rest in. They're best to order when you can perch on a nearby curb or bench and snarf them right away.

Tasting notes: A trio of toppings—caramelized onions and shallots, giardiniera and house-made cheddar sauce that's miles away from the bright-orange food-court variety—makes this sloppy serving of fries a creamy-spicy-sweet flavor bomb. The fries could stand to be a little crispier to stand up to all the toppings, but that was my only gripe.

Also serving: A twisted reuben sandwich with crispy pastrami and tarragon slaw and grilled salami on a pretzel bun with pickled onions, barbecue sauce and a fried egg

Track the truck: thefatshallot.com or @thefatshallot on Twitter

Reporters visit food trucks unannounced and meals are paid for by RedEye.